Various cards, such as microfiche cards, microfilm jackets and aperture cards are stored in trays or drawers. It is common practice to use compressors or followblocks to keep the cards compressed in a compact, vertical position within the drawer.
One common form of compressor is fitted into a track in the bottom of the drawer in such a manner as to be adjustable lengthwise so as to hold different numbers of cards in a vertical orientation. One limitation of this kind of compressor is that the compressor must be released and pushed away from the cards in order to gain access to one or more of the cards. Following this, the compressor must be readjusted up against the cards to hold them in the vertical position. Because of this inconvenience, this type of compressor is most often employed with files which are not used frequently.
In more active card files, wobble blocks or rigid dividers which could be inclined forward and backward in a "V" angle are used. However, with wobble blocks, filing space is lost due to the inability to fully use the space between the wobble blocks.
In another prior art compressor, the compressor is magnetically retained on the bottom of the drawer and has a compressor member spring biased to a forward position to engage the cards and retain them in a vertical position. One problem with this compressor is that the compressor member must be manually held in a rearward position in order to gain access to the cards, and this leaves only one hand free to locate and withdraw the card or cards or interest.